Separable seal assembly for a gas turbine engine

ABSTRACT

A seal assembly for sealing a rotatable shaft in a gas turbine engine, wherein the shaft includes sections of greater shaft diameter located both forward and aft of the seal shaft coupling point is provided. The seal assembly includes a first semi-annular segment with a first end, a second end, and a plurality of seal teeth, where the first and second ends each include an overlap joint. The seal assembly also includes a second semi-annular segment with a first end, a second end, and a plurality of seal teeth, where the first and second ends each include an overlap joint. The first end of the second segment is coupled to the first end of the first segment, and the second end of the second segment is coupled to the second end of the first segment.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/639403, filed Apr. 27, 2012, which is incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

The field of the invention relates generally to gas turbines, and moreparticularly to methods and a system for a seal assembly for aninter-shaft seal in a gas turbine engine.

Labyrinth seals are widely used on rotatable shafts to regulatesecondary air flows and provide a radial clearance between low speedshafts and high speed shafts in gas turbine engines. Generally, in moredetail, the seals include a series of parallel teeth that facilitateregulating a flow past the teeth and capturing any excess oil. The tipsof the teeth provide the clearance between the two shafts. Newergeneration engines include shafts made of strong, but brittle materialsthat may not be as tolerant of the rubbing that typical seal teethendure during engine operation. The rubbing can cause localizedmicro-cracking in the shaft. Seals made of a single unit that areintegral to the shaft may not be allowable in some situations due tomaterial or stress concerns. Additionally, sections of greater shaftdiameter located both forward and aft of the seal can preventimplementation of the seal on an unbroken ring of material. Accordingly,a seal that is separable and not subject to the torque load of theshaft, which results in greater flexibility in design at a lower costfor repair and maintenance is desirable.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a seal assembly for sealing a rotatable shaft in a gasturbine engine, wherein the shaft includes sections of greater shaftdiameter located both forward and aft of the seal shaft coupling pointis provided. The seal assembly includes a first semi-annular segmentwith a first end, a second end, and a plurality of seal teeth, where thefirst and second ends each include an overlap joint. The seal assemblyalso includes a second semi-annular segment with a first end, a secondend, and a plurality of seal teeth, where the first and second ends eachinclude an overlap joint. The first end of the second segment is coupledto the first end of the first segment, and the second end of the secondsegment is coupled to the second end of the first segment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary gas turbine engineassembly for use in propelling an aircraft.

FIG. 2 is an enlarged cross-sectional view of the exemplary seal shownin FIG. 1 in relation to the first and second shafts.

FIG. 3 is a perspective view of an exemplary seal in accordance with thepresent invention.

FIG. 4 is a cross-sectional view of the seal on the first shaft taken atline 4-4 in FIG. 3.

FIG. 5 is a perspective view of an alignment pin connecting the twosegments of the seal shown in FIGS. 3 and 4.

FIG. 6 is a perspective view of an alternate embodiment of the seal inaccordance with the present invention.

FIG. 7 is a cross-sectional view of the seal on the first shaft taken atline 7-7 in FIG. 6.

FIG. 8 is a perspective view of an alternate embodiment of the seal inaccordance with the present invention.

FIG. 9 is a cross-sectional view of the seal on the first shaft taken atline 9-9 in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description illustrates an inter-shaft seal and amethod of assembling the same by way of example and not by way oflimitation. The description enables one of ordinary skill in the art tomake and use the disclosure, and the description describes severalembodiments of the disclosure, including what is presently believed tobe the best mode of carrying out the disclosure. The disclosure isdescribed herein as being applied to a preferred embodiment, namely, aninter-shaft seal and a method of assembling the same. However, it iscontemplated that this disclosure has general application to shaft sealsin a broad range of systems and in a variety of industrial and/orconsumer applications.

FIG. 1 is a cross-sectional view of an exemplary gas turbine engine(GTE) 10. GTE 10 includes a fan assembly 12, a core gas turbine enginesection 14 coupled downstream from fan assembly 12, and a low-pressureturbine 16 coupled downstream from the core gas turbine engine section14. In the exemplary embodiment, core gas turbine engine section 14includes a multi-stage booster compressor 18, a high-pressure compressor20, a combustor 22, and a high-pressure turbine 24. GTE 10 also includesan inlet 26 and an exhaust 28. In the exemplary embodiment, low-pressureturbine 16 and booster compressor 20 are coupled together via a firstdrive shaft 30, and compressor 18 and high-pressure turbine 24 arecoupled together via a second drive shaft 32.

In operation, air is drawn into engine inlet 26, and compressed throughbooster compressor 18 and high pressure compressor 20. The compressedair is channeled to combustor 22 where it is mixed with fuel and ignitedto produce air flow through high pressure turbine 24 and low pressureturbine 16, and exits through exhaust 28.

FIG. 2 is an enlarged cross-sectional view of the gas turbine engineshown in FIG. 1. GTE 10 includes a seal 34 coupled to first shaft 30.Seal 34 is separable from shaft 30 and includes at least two segmentssuch that it may be installed or removed on a complete shaft withoutneeding clearance on either end of the shaft. Moreover, being made of atleast two segments facilitates installation of seal 34 on a shaft evenwhen the shaft has a greater diameter on both sides of seal 34installation point, which provides much greater flexibility in whereseal 34 is located on a shaft. Seal 34 may include, as desired,labyrinth tooth material of the same material, or different material,as/than the shaft 30, respectively. Seal 34 may be coupled to shaft 30in multiple ways, which are described below.

FIG. 3 is a perspective view of an exemplary seal 34 in accordance withthe present invention. Seal 34 includes a first half circle-shapedsegment 300 and a second half circle-shaped segment 302. First segment300 includes a first end having a connector 304 and a second end havinga connector 306. Second segment 302 includes a first end having aconnector 308 and a second end having a connector 310. First segment 300and second segment 302 assemble by an overlap joint, by joiningconnectors 304 and 308, and connectors 306 and 310. The overlap jointallows seal 34 to carry a hoop load. Segments 300 and 302 each include aplurality of seal teeth 312.

FIG. 4 is a cross-sectional view of seal 34 (shown in FIG. 3) coupled toa shaft taken at line 4-4 in FIG. 3. In the exemplary embodiment, theshaft is shaft 30 (shown in FIG. 1). The primary retention for seal 34is an interference fit between seal 34 and a shoulder 400 of shaft 30.First segment 300 includes a shoulder 402 (shown in FIG. 3) that enablessecondary axial and tangential retention on shaft 30.

Assembly of first and second segments 300 and 302 about shaft 30 isaccomplished by heating both first and second segments 300 and 302 to apredetermined temperature, sliding first segment 300 in from a side ofshaft 30, and sliding second segment 302 axially such that connectors308 and 310 engage the mating halves of connectors 304 and 306,respectively. When allowed to equalize in temperature with shaft 30, aninterference fit is generated between first and second segments 300 and302 and shaft 30. First and second segments 300 and 302 enable the ringformed by their coupling to carry hoop stress. To hold first and secondsegments 300 and 302 together, a retaining ring 404 is expanded into aslot 406. Moreover, with reference to FIG. 5, an alignment pin 500 isplaced in an alignment orifice 502 formed between first and secondsegments 300 and 302 (shown in FIGS. 3 and 4). Alignment pin 500 is thentrapped by the retaining ring, which is installed last.

FIG. 6 is a perspective view of an alternative embodiment of seal 34 inaccordance with the present invention. Seal 34 includes first inner ringsegment 600, second inner ring segment 602, first outer ring segment604, and second outer ring segment 606. First and second inner ringsegments 600 and 602 are similar to first and second segments 300 and302, as described in FIGS. 3-5, less the retaining ring, and are coupledto a shaft in the same manner. Seal 34 also includes first outer ringsegment 604 and second outer ring segment 606 coupled together aboutfirst and second inner ring segments 600 and 602. Outer ring segments604 and 606 each include a plurality of seal teeth 608.

FIG. 7 is a cross-sectional view of seal 34 on shaft 30 (shown inFIG. 1) taken at line 7-7 in FIG. 6. The primary retention of seal 34 isaccomplished by an interference fit to shaft 30, and secondary axialretention is accomplished by protrusions 701 on the inner diameter ofseal 34 on either side of a shoulder 700 of shaft 30. Secondarytangential retention is provided by a tab 702 which engages with akeyway 704 on shaft 30. The four ring segments 600, 602, 604, and 606are coupled along two 360 degree seams 708 between the segments.Segments 600, 602, 604, and 606 may be coupled by welding and brazing.

Assembly of first and second segments 600 and 602 about shaft 30 isaccomplished by heating both first and second inner ring segments 600and 602, sliding first inner ring segment 600 in from the side, andsliding second inner ring segment 602 axially such that connector 610engages the mating half of connector 612, and another set of connectors(not shown) engage on the other side of seal 34. When allowed toequalize in temperature with shaft 30, an interference fit is generatedbetween first and second inner ring segments 600 and 602 and shaft 30,enabling segments 600 and 602 to carry hoop stress. Following thisinitial assembly step, two 180 degree segments, first outer ring segment604 and second outer ring segment 606, are coupled to the ring createdby first and second inner ring segments 600 and 602, and welded inplace. The weld joint is formed along the two 360 degree seams betweenouter ring segments 604 and 606, and inner ring segments 600 and 602.Seal teeth 608 are finish machined following assembly and welding ofsegments 600, 602, 604, and 606 to ensure tooth alignment and tip runoutrequirements are met.

FIG. 8 is a perspective view of an alternate embodiment of seal 34 inaccordance with the present invention. FIG. 9 is a cross-sectional viewof separable seal 34 on a shaft taken at line 9-9 in FIG. 8. Seal 34 iscomprised of a plurality of identical segments 800. In the exemplaryembodiment, seal 34 includes four identical segments 800. Segments 800are connected to shaft 30 (shown in FIG. 1) by a dovetail joint.Segments 800 each include a plurality of seal teeth 802.

Segments 800 are assembled about shaft 30 (shown in FIG. 1) by insertingthem through a load slot 804 in shaft 30. Segments 800 are then rotatedaround load slot 804 until all segments 800 are in place. For eachsegment 800, a set screw (not shown) is installed through a tapped hole806 located in each segment 800. The screw engages with a dimple 900 inshaft 30 to provide secondary retention. Each segment 800 has only adovetail pressure face over the central 50% of its arc length, allowingload slot 804 to be smaller in size.

The seal assembly described herein enables installation of a separableseal on a shaft where integral teeth and/or a one piece ring are notusable. The seal assembly provides a 360 degree ring that can beinstalled on a completed shaft without needing clearance on either endfor installation. The assembly provides different connection optionsdepending on the specifications required.

While multiple inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the invent of embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

Examples are used to disclose the embodiments, including the best mode,and also to enable any person skilled in the art to practice theapparatus and/or method, including making and using any devices orsystems and performing any incorporated methods. These examples are notintended to be exhaustive or to limit the disclosure to the precisesteps and/or forms disclosed, and many modifications and variations arepossible in light of the above teaching. Features described herein maybe combined in any combination. Steps of a method described herein maybe performed in any sequence that is physically possible.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms. The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.” The phrase“and/or,” as used herein in the specification and in the claims, shouldbe understood to mean “either or both” of the elements so conjoined,i.e., elements that are conjunctively present in some cases anddisjunctively present in other cases.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is:
 1. A seal assembly for sealing a rotatable shaft ina gas turbine engine comprising: The rotatable shaft comprising sectionsof greater shaft diameter located both forward and aft of the seal shaftcoupling point, said seal assembly comprising: a first semi-annularsegment comprising a first end, a second end, and a plurality of sealteeth, said first and second ends each including an overlap joint; and asecond semi-annular segment comprising a first end, a second end, and aplurality of seal teeth, said first and second ends each including anoverlap joint, said first end of said second segment being coupled tosaid first end of said first segment, and said second end of said secondsegment being coupled to said second end of said first segment.
 2. Theseal assembly of claim 1 further comprising: a seal coupled to a firstshaft, the seal being separable from the shaft and including at leasttwo segments; the seal being capable of being installed or removed on acomplete shaft without a need to provide clearance on either end of theshaft; the at least two segments facilitating installation of the sealon the shaft to include shafts having a greater diameter on both sidesof a seal installation point, thereby providing a multiplicity ofchoices for location of the seal with respect to the shaft.
 3. A sealassembly for sealing a rotatable shaft in a gas turbine enginecomprising: The shaft comprising sections of greater shaft diameterlocated both forward and aft of the seal shaft coupling point, said sealassembly comprising: a first half circle-shaped segment and a secondhalf circle-shaped segment; the first segment including a first endhaving a connector and a second end having a connector; and, the secondsegment including a first end having a connector and a second end havinga connector.
 4. The seal assembly of claim 3 further comprising: Thefirst segment and the second segment being assembled by an overlapjoint, wherein mating connectors and, are joined with co-matingconnectors; and, the overlap joint thereby allowing the seal to carry ahoop load.
 5. The seal assembly of claim 4 further comprising segments,each segment including a plurality of seal teeth.
 6. The seal assemblyof claim 5 further comprising a primary retention for the seal being aninterference fit between seal and a shoulder of shaft wherein the firstsegment includes a shoulder that enables secondary axial and tangentialretention on the shaft.
 7. The seal assembly of claim 6 furthercomprising the assembly of the first and second segments and about theshaft being accomplished by heating both the first and the secondsegments to a predetermined temperature, sliding first segment in from aside of shaft, and sliding second segment axially such that theconnectors of one segment engage the mating halves of connectors on theother segment, respectively.
 8. The seal assembly of claim 7 furthercomprising allowing temperature to equalize within the shaft therebyproviding an interference fit being generated between first and secondsegments and shaft; the first and second segments enabling the ringformed by their coupling to carry hoop stress; the first and secondsegments being secured together by a retaining ring that is expandedinto a slot; an alignment pin being placed in an alignment orifice thatis disposed between the first and second segments; and, the retainingring being installed last, thereby securing the alignment pin.
 9. A sealassembly for sealing a rotatable shaft in a gas turbine enginecomprising: the shaft comprising sections of greater shaft diameterlocated both forward and aft of the seal shaft coupling point; and, saidseal assembly comprising a first inner ring segment, a second inner ringsegment, a first outer ring segment, and a second outer ring segment.10. The seal assembly of claim 9 further comprising the first outer ringsegment and the second outer ring segment coupled together about firstand second inner ring segments and wherein the outer ring segments andeach include a plurality of seal teeth.
 11. The seal assembly of claim10 further comprising the primary retention of seal being accomplishedby an interference fit to shaft, and secondary axial retention beingaccomplished by protrusions on the inner diameter of seal on either sideof a shoulder of shaft.
 12. The seal assembly of claim 11 furthercomprising that secondary tangential retention is provided by a tabwhich engages with a keyway on the shaft; The four ring segments arecoupled along two 360 degree seams between the segments; and, thesegments being coupled by a securing method chosen from the groupwelding, brazing.
 13. The seal assembly of claim 12 further comprisingthat an initial assembly of first and second segments and about shaft isaccomplished by: heating both first and second inner ring segments;sliding first inner ring segment in from the side, and sliding secondinner ring segment axially such that connector engages the mating halfof connector, while a corresponding set of connectors engages in asimilar fashion on the other side of the seal; and, When allowed toequalize in temperature with shaft, an interference fit is generatedbetween first and second inner ring segments and shaft, enablingsegments to carry hoop stress.
 14. The seal assembly of claim 13 furthercomprising that following the initial assembly steps of claim 13: two180 degree segments being the first outer ring segment and the secondouter ring segment, are coupled to the ring created by first and secondinner ring segment; the 180 degree segments being welded in placewherein the weld joint is formed along two 360 degree seams between theouter ring segments, and the inner ring segments; and, Seal teeth arefinish machined following assembly and welding of segments therebyensuring that tooth alignment and tip runout requirements are met.
 15. Aseal assembly for sealing a rotatable shaft in a gas turbine enginecomprising: the shaft comprising sections of greater shaft diameterlocated both forward and aft of the seal shaft coupling point; and, saidseal assembly comprising a plurality of identical segments.
 16. The sealassembly of claim 15 further comprising the plurality being fouridentical segments connected to the shaft by a dovetail joint andwherein each segment includes a plurality of seal teeth.
 17. The sealassembly of claim 16 further comprising that assembly of segments aboutthe shaft is accomplished by: inserting the segments through a load slotformed in the shaft; and, rotating the segments around the load slot,repeating until all segments are in place.
 18. The seal assembly ofclaim 17 further comprising installing a set screw through a tapped holelocated in each segment.
 19. The seal assembly of claim 18 wherein theset screw engages with a dimple in shaft thereby providing secondaryretention.
 20. The seal assembly of claim 15 wherein each segment hasformed upon it a dovetail pressure face over a central 50% of its arclength, thereby allowing a corresponding reduction in the size of theload slot.